UPDATE 1-Amec Foster Wheeler appoints Halliburton executive as CEO

* Revenue, order book value fall in first quarter (Adds details, background)

By Karolin Schaps

LONDON, April 27 (Reuters) - British oil and gas services company Amec Foster Wheeler said it has appointed Halliburton executive Jonathan Lewis as chief executive on Wednesday, replacing long-serving CEO Samir Brikho who left unexpectedly in January.

Lewis will take up his role on June 1 and interim chief executive Ian McHoul will return to his role as chief financial officer full time, the engineering firm said.

Lewis, who will receive an annual base salary of 775,000 pounds ($1.13 million) takes over at a company facing record-low investments from its key oil and gas customers amid weak oil prices.

His main priority will be to reach the company's target to halve debt before June 2017 and to boost investor confidence in the company after it chopped its dividend at the end of last year.

Amec said in a trading update on Wednesday that it expected a slight decline in revenue this year and that net debt was expected at 1 billion pounds ($1.46 billion) by the end of the year, roughly in line with end-2015 levels.

It also reported a 1.5 percent fall in first-quarter revenue to 1.3 billion pounds and said its order book had shrunk 3 percent to 6.4 billion pounds over the first three months of the year.

Amec said it was in negotiations with a number of interested buyers for its Global Power Group, which it put up for sale earlier this year.

"Other businesses/assets that have been identified as non-core are also being prepared for sale," the company said. ($1 = 0.6862 pounds)